1. Field of the Invention.
This invention pertains to the use of cleanser or detergent formulations and solutions as waste water and water recycling treating solutions for reducing solids, heavy metals and oils in waste water. The invention particularly relates to a detergent formulation the, when properly used, cleans equipment and materials while simultaneously cleaning waste waters before discharge and increasing the efficiency of water recycling systems.
2. Description of the Prior Art.
Increasing restrictions on waste water effluents are forcing producers of such effluents to find ways either to recycle or clean such waters. These restrictions affect not only food processing and industrial plants, but also the cleaning of equipment within such plants. Particularly, the amount of effluent wash water produced during the clean up of equipment such as trucks which require the use of cleaning compounds for proper cleaning are restricted. Manufacturing processes which use water are limited to recycled effluent waters used in such processing.
In the past, processing and wash waters were dumped directly into the sewers or storm drains. Increasing concentrations of pollutants are being found in ground and fresh water systems. Some of these pollutants can be traced to processing plants and equipment clean up.
In order to limit such pollutants, industries have initiated plans for recycling and cleaning waste water effluents. Clean up of processing waste water mainly consists of filtration, flocculation and neutralization. These programs have met with limited success.
Neutralization of waste water is perhaps the most successful form of water discharge. However, neutralization is limited to balancing the pH of waste water for discharge and doesn't eliminate pollutants. Filtration can eliminate undissolved particles but will not remove pollutants which are dissolved in the water. Flocculation will eliminate some, but not all, pollutants, and requires space and time. Also, many flocculants are equally or more hazardous to the environment as the eliminated pollutants.
Recycled waste water is becoming more attractive to industry. Subsequently, waste water recycling equipment is increasingly important, particularly in the reuse of washing and processing equipment. However, water used for processing and equipment wash-downs needs to be treated. Industry generally uses soaps or detergents to wash equipment. The waste water from such processes and washes then is treated both mechanically and chemically through recycling equipment.
Theoretically, such waste water goes through a recycler. Chemicals and mechanical action cause the dirt and undissolved particles to deposit as a sludge and to float oils to be skimmed. The subsequent water should be clean enough to be reused in the same process or to be discharged into the environment. Sludge and oils are removed periodically from the water recycling equipment. In a non-recycling scheme, the chemically and mechanically treated water should be clean enough for discharge.
However, water used with soap or detergent alone, does not clean or recycle well. Most detergents and soaps use a caustic soda base for cleaning which ties up oils and heavy metals. Detergent and soap formulations emulsify oil and suspend it so well that it is difficult to separate the waste components from the water to be recycled or discharged. This can result in the physical blockage of any mechanical actions that would have aided in waste water clean up. Additionally, such soaps and detergents increase the microbial growth in the waste water or waste water recycling equipment, causing blockage of baffles and filters and creating odor emissions. Microbial growth is a major factor in the failure of waste water recycling units. Most soaps, detergents and cleaners contribute to microbial growth in waste water treating systems.
Recycled or discharged Industrial cleaners are made of the following basic components:
______________________________________ Cleaner component Purpose ______________________________________ Sodium Hydroxide Cleaning agent Sodium Metasilicate Pentahydrate Alkalinity builder and cleaning agent Glycol Ether Oil emulsifier Phosphates Water softener EDTA and/or NTA Water softener Carboxymethylcellulose Clinging and thickening agent Surfactants Surface tension reduction and penetrating agent Hydrotrope Phosphate Ester Formula stratification inhibitor ______________________________________
These components, however, present special problems in water recycling equipment. Sodium hydroxide increases the pH of the water and emulsifies the oils so well that the oils will not separate from the water in the recycling equipment. Sodium hydroxide also contributes to scaling (calcium build-up) of equipment and water spots upon drying.
Sodium metasilicate pentahydrate builds alkalinity, which acts as a buffer, and contains sodium hydroxide, which increases oil emulsification. A glycol ether further causes oil emulsification making oil separation more difficult.
To counteract the negative effect of such cleaners on waste water treating systems, users must treat the waste water with some or all of the following types of chemicals: polymers, pH adjusting chemicals and bleach.
Cationic and anionic polymers are charged such that dissolved and undissolved particles precipitate or "floc" out of the water. Such precipitation of "dirt" collects as a sludge for later removal. However, polymers can cause microbial growth and leave a hazardous residue in the "cleaned" water. Finally, a polymer's efficiency can be limited, depending on the content of the waste water.
PH adjusting chemicals, such as caustic soda, aid in the precipitation of heavy metals such as lead, cadmium, chrome, and nickel. Yet, heavy metals precipitate over a narrow specific pH range for each specific metal thereby requiring constant pH adjustment. Typical pH adjusting chemicals also tie up oils, making oil-water separation more difficult.
EDTA is also used for heavy metal collection. However, harmful residues may emerge from the waste water treatment equipment and be found in the discharge water.
Bleach is often used as a last resort to kill unwanted microbial growth in waste water treating systems. This method is inefficient and causes chlorine residues in the recycled or discharged water.